Surgical cassette having an aspiration pressure sensor

ABSTRACT

A cassette having a molded flow channel contained on an elastomeric sheet that is bonded or mechanically attached to a rigid substrate. The flow channel projects outwardly from the exterior of the cassette so that a peristaltic pump having pump head rollers mounted radially from the axis of rotation of the pump motor compress the elastomeric flow channels against the rigid substrate during operation.

This application is a continuation of U.S. patent application Ser. No.10/407,388 , filed Apr. 4, 2003, now U.S. Pat. No. 6,962,488 B2 which isa continuation-in-part application of U.S. patent application Ser. No.09/846,724, filed May 1, 2001, now U.S. Pat. No. 6,572,349 B2 which is acontinuation of U.S. patent application Ser. No. 09/437,392, filed Nov.10, 1999, now U.S. Pat. No. 6,293,926 B1, and a continuation-in-part ofU.S. patent application Ser. No. 10/153,371, filed May 28, 2002, nowU.S. Pat. No. 6.902,542 B2.

BACKGROUND OF THE INVENTION

The present invention relates generally to peristaltic pumps and morespecifically to peristaltic pumps used in ophthalmic surgical equipment.

Most prior art peristaltic pumps work by compressing or squeezing alength of flexible tubing (sometimes between a fixed race) using arotating roller head. As the roller head rotates, the rollers pinch offa portion of the tubing and push any fluid trapped in the tubing betweenthe rollers in the direction of rotation. Peristaltic pumps are widelyused in medical applications because of their predictable, constant flowproperties. These prior art systems, however, typically require manualconnection of the pump tube segment around the rotating roller head.

Prior art peristaltic pumps using rotating roller heads also typicallyimpart unwanted pressure pulsations. Several pulsation damping deviceshave been developed to address this problem (see e.g., U.S. Pat. No.4,921,477 (Davis)).

Accordingly, a need continues to exist for a peristaltic pump thatreduces pressure pulsations and that is simpler and more economical tomanufacture and use.

BRIEF SUMMARY OF THE INVENTION

The present invention improves upon prior art peristaltic pumps byproviding a cassette having a molded flow channel contained on anelastomeric sheet that is bonded or mechanically attached to a rigidsubstrate. The cassette is used in combination with a peristaltic pumphaving pump head rollers that are mounted radially from the axis ofrotation of the pump motor so as to compress the elastomeric flowchannels against the rigid substrate during operation.

One objective of the present invention is to provide a cassette thatuses molded elastomeric flow channels.

Another objective of the present invention is to provide a cassette fora peristaltic pump having radially oriented pump rollers.

Yet another objective of the present invention is to provide a cassettefor a peristaltic pump having pump rollers that compress elastomericflow channels in the cassette against a rigid substrate.

These and other advantages and objectives of the present invention willbecome apparent from the detailed description, drawings and claims thatfollow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic top plan view of a first embodiment of the presentinvention, with the motor and roller head removed for clarity.

FIG. 2 is a schematic side elevational view of a first embodiment of thepresent invention, with the motor and roller head removed for clarity.

FIG. 3 is a cross-sectional view of the first embodiment of the presentinvention taken at line 3-3 in FIG. 1.

FIG. 4 is a schematic top plan view of a second embodiment of thepresent invention, with the motor and roller head removed for clarity.

FIG. 5 is a schematic side elevational view of a second embodiment ofthe present invention, with the motor and roller head removed forclarity.

FIG. 6 is a schematic front elevational view of a second embodiment ofthe present invention, with the motor and roller head removed forclarity.

FIG. 7 is a perspective view of a third embodiment of the cassette ofthe present invention.

FIG. 8 is a perspective view of a surgical console that may be used withthe present invention.

FIG. 9 is a perspective view of a fourth embodiment of the cassette ofthe present invention.

FIG. 10 is a perspective view of a fifth embodiment of the cassette ofthe present invention.

FIG. 11 is a perspective view of the cassette of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

As best seen in FIGS. 1, 2 and 3, in a first embodiment of the presentinvention, pump 10 of the present invention generally includes pumpmotor 12, roller head 14, containing one or more rollers 16 and cassette18 having elastomeric sheet 20 applied to the exterior of relativelyrigid body or substrate 22. Pump motor 12 preferably is a stepper orD.C. servo motor. Roller head 14 is attached to shaft 24 of motor 12 sothat motor 12 rotates roller head 14 in a plane generally normal to axis25 of shaft 24, and the longitudinal axes of rollers 16 are generallyradial to axis 25 of shaft 24.

Sheet 20 contains molded fluid channel 26 that is generally planar,arcuate in shape (within the plane) and having a radius approximatingthat of rollers 16 about shaft 24. Fluid channel 26 fluidly connectsports 28 and 30. Sheet 20 may be made of any suitably flexible, easilymolded material such as silicone rubber or thermoplastic elastomer.Sheet 20 is attached or bonded to substrate 22 by any suitable techniquesuch as adhesive, heat fusion or mechanical crimping. Substrate 22preferably is made of a material that is rigid with respect to sheet 20,such as a rigid thermoplastic, and may be made by any suitable method,such as machining or injection molding.

In use, cassette 18 is held in close proximity to roller head 14 so thatrollers 16 compress channel 26 against substrate 22 as roller head 14rotates. The longitudinal axes of the rollers are arranged so thatroller 16 contact with channel 26 is generally parallel with the planeof channel 26. Such an arrangement eliminates the need to loop a lengthof flexible tubing over the pump roller head and thus simplifies theloading of pump channel 26 against pump roller head 14. Rollers 16 maybe tapered along their axial length to accommodate the difference inpath length traveled by the inner and outer sections of rollers 16 asroller head 14 rotates. Unwanted pressure pulsations could be minimizedby providing channel transition regions 46 and 47 having internalcross-sections that taper from zero to the full cross-section of channel26. These regions minimize the abrupt change in displaced volume asrollers 16 transition on or off of channel 26.

As best seen in FIGS. 4-6, in a second embodiment of the presentinvention, cassette 18′ may contain additional fluid channels thatprovide control of irrigation fluid as well as aspiration fluid. Forexample, cassette 18′ may contain aspiration inlet port 32 andaspiration outlet port 34 that are connected through channel 26′.Upstream of port 32, cassette 18′ may contain aspiration pressure sensorinterface 36, which may be any of a variety of non-invasive pressuresensors such as those disclosed in U.S. Pat. No. 5,910,110 (Bastable)and U.S. Pat. No. 5,470,312 (Zanger, et al.), the entire contents ofwhich being incorporated herein by reference. Cassette 18′ may alsocontain a vent pinch valve site 38 for allowing the venting of anyvacuum from channel 26′. Irrigation fluid enters cassette 18′ throughport 40 and exits cassette 18′ through port 42 and is controlled byvalve or pinch valve site 44, which may be actuated by a plunger (notshown). Vent 38 may be operated in a similar method. In addition,between port 40 and irrigation pinch valve site 44, cassette 18′ maycontain irrigation pressure interface 50. Pressure interface 50 may bemade from a thin molded membrane contained within elastomeric sheet 20′over a fluid chamber (not shown) contained within substrate 22′. Such aninterface allows detection of irrigation pressure in a non-invasivemanner using a surface contact pressure transducer or calibrated loadcell.

As best seen in FIG. 7, cassette 18″ of the present invention containsaspiration pressure sensor interface 36″. Interface 36″ may consist ofthin diaphragm 37 preferably made of metal or rigid plastic. An externalloadcell (not shown) located on console 80 is used to deflect diaphragm37 to a predetermined initial force load. Changes in pressure on theinternal side of diaphragm 37 opposite the loadcell will cause a changein force on the loadcell that can be correlated to the pressure level oninterface 36″. The inventors have discovered that forces on cassette 18″during use can cause flexing of substrate 22″. Such flexing can causeinaccurate reading from the load cell used in conjunction with pressuresensor interface 36″. In order to minimize such inaccuracies, substrate22″ contains a raised boss 60 around pressure sensor interface 36″. Whensubstrate 22″ is clamped in place against a rigid mounting member (notshown) on console 80, boss 60 helps to stabilize the area aroundpressure sensor interface 36″ and isolate pressure sensor interface 36″from forces acting on other regions of substrate 22″. In addition,cassette 18″ may contain one or more plurality of latching surfaces 90per side that cooperate with a latching mechanism, such as the latchingmechanism described in commonly-owned U.S. patent application Ser. No.10/132,797, filed Apr. 25, 2002, to assist in holding cassette 18″firmly within console 80 further reducing the possibility of flexing ofcassette 18″. Latching surfaces 90 preferably are located along sides 92of substrate 22″ and preferably, are formed as indentations within sides92 of substrate 22″. Such a construction helps to prevent thepossibility of the latching mechanism capturing the finger of a user.Alternatively, as shown in FIGS. 9-10, cassette 118 can have continuouslatching surfaces 90′ with (FIG. 9) or without (FIG. 10) finger pinchprotective cover 94. Cassette 118 preferably has handle 360 that isaligned near the axis of the pump roller head. Such a construction easesthe insertion of cassette 118 into the latching mechanism.

Cassette 18″ that may be used with pump 10 of the present invention mayalso contain a plurality of identifying tabs 70 projecting from housingsubstrate 22″. Tabs 70 may be generally of the shape described in U.S.Pat. No. 6,059,544 (Jung, et al.) and may be of variable opaqueness,from completely opaque to partially translucent to relatively clear. Theopaqueness of tabs 70 may be used by console 80 (as seen in FIG. 8) toidentify the particular cassette 18″ being used from a variety ofsuitable cassette 18″ in a manner similar to that disclosed in U.S. Pat.No. 6,059,544 (Jung, et al.), the entire contents of which beingincorporated herein by reference.

As best seen in FIG. 11, cassette 218 may contain one or more alignmentfeatures, such as indentations 300 that match corresponding alignmentfeatures (not shown) on console 80. One skilled in the art willrecognize that instead of indentation 300, protrusions (not shown) maybe used alternatively. Indentations 80 assure that cassette 218 islocated properly within console 80, rotationally, vertically andhorizontally. Indentations 80 may be located on either side of cassette218.

In addition, pressure sensor well 335 has aspiration exit port 340located above bottom 338 of well 335. Such a construction allows anysolid material flowing into well 335 through port 340 to precipitatedown to bottom 338 of well 335. Port 340 is also located in the middleof well 335 so as not to draw precipitated material on bottom 338 intoport 340 during reverse flow situations, such as venting or reflux.Cassette 218 may contain one or more auxiliary vent port(s) 350 thatprovides redundant venting paths in case port 340 becomes clogged.

This description is given for purposes of illustration and explanation.It will be apparent to those skilled in the relevant art thatmodifications may be made to the invention as herein described withoutdeparting from its scope or spirit.

1. A cassette, comprising: a) a body having an exterior; b) a relativelyflexible sheet attached to the body, the sheet containing at least onemolded fluid channel, the fluid channel projecting outwardly from theexterior of the body and being in a generally arcuate shape; c) anaspiration pressure sensor interface on the exterior of the body; and d)a raised boss around the pressure sensor interface.
 2. The cassette ofclaim 1 wherein the sheet comprises a molded aspiration fluid channeland a molded irrigation fluid channel.
 3. The cassette of claim 1wherein the sheet comprises a flexible, easily molded material.
 4. Thecassette of claim 3 wherein the sheet comprises silicone rubber orthermoplastic elastomer.
 5. The cassette of claim 1 wherein the fluidchannel is planar.
 6. The cassette of claim 1 wherein the fluid channelhas at least one transition region wherein the cross-sectional area ofthe fluid channel tapers.
 7. The cassette of claim 1 wherein the fluidchannel has at least one pinch valve site.
 8. The cassette of claim 1wherein the cassette further comprises a plurality of identifying tabsprojecting from the exterior of the body.
 9. A cassette, comprising: a)a body having an exterior; b) a relatively flexible sheet attached tothe body, the sheet containing at least one molded fluid channel, thefluid channel projecting outwardly from the exterior of the body andbeing in a generally arcuate shape and containing at least one pinchvalve site; c) an aspiration pressure sensor interface on the exteriorof the body; d) a raised boss around the pressure sensor interface; ande) a plurality of identifying tabs projecting from the exterior of thebody.
 10. The cassette of claim 9 wherein the sheet comprises a moldedaspiration fluid channel and a molded irrigation fluid channel.
 11. Thecassette of claim 9 wherein the sheet comprises a flexible, easilymolded material.
 12. The cassette of claim 11 wherein the sheetcomprises silicone rubber or thermoplastic elastomer.
 13. The cassetteof claim 9 wherein the fluid channel is planar.
 14. The cassette ofclaim 9 wherein the fluid channel has at least one transition regionwherein the cross-sectional area of the fluid channel tapers.
 15. Acassette, comprising: a) a body having an exterior, the exterior havingsides; b) a relatively flexible sheet attached to the body, the sheetcontaining at least one molded fluid channel, the fluid channelprojecting outwardly from the exterior of the body and being in agenerally arcuate shape; c) an aspiration pressure sensor interface onthe exterior of the body; and d) a plurality of latching surfaces formedin the sides of the body.
 16. The cassette of claim 15 wherein the sheetcomprises a molded aspiration fluid channel and a molded irrigationfluid channel.
 17. The cassette of claim 15 wherein the sheet comprisesa flexible, easily molded material.
 18. The cassette of claim 17 whereinthe sheet comprises silicone rubber or thermoplastic elastomer.
 19. Thecassette of claim 15 wherein the fluid channel is planar.
 20. Thecassette of claim 15 wherein the fluid channel has at least onetransition region wherein the cross-sectional area of the fluid channeltapers.
 21. The cassette of claim 15 wherein the fluid channel has atleast one pinch valve site.
 22. The cassette of claim 15 wherein thecassette further comprises a plurality of identifying tabs projectingfrom the exterior of the body.
 23. A cassette, comprising: a) a bodyhaving an exterior, the exterior having sides; b) a relatively flexiblesheet attached to the body, the sheet containing at least one moldedfluid channel, the fluid channel projecting outwardly from the exteriorof the body and being in a generally arcuate shape and containing atleast one pinch valve site; c) an aspiration pressure sensor interfaceon the exterior of the body; d) a raised boss around the pressure sensorinterface; e) a plurality of identifying tabs projecting from theexterior of the body; and f) a plurality of latching surfaces formed inthe sides of the body.
 24. The cassette of claim 23 wherein the sheetcomprises a molded aspiration fluid channel and a molded irrigationfluid channel.
 25. The cassette of claim 23 wherein the sheet comprisesa flexible, easily molded material.
 26. The cassette of claim 25 whereinthe sheet comprises silicone rubber or thermoplastic elastomer.
 27. Thecassette of claim 23 wherein the fluid channel is planar.
 28. Thecassette of claim 23 wherein the fluid channel has at least onetransition region wherein the cross-sectional area of the fluid channeltapers.
 29. A cassette, comprising: a) a body having an exterior; b) arelatively flexible sheet attached to the body, the sheet containing atleast one molded fluid channel, the fluid channel projecting outwardlyfrom the exterior of the body and being in a generally arcuate shape; c)an aspiration pressure sensor interface on the exterior of the body, theinterface having a well; and d) an aspiration exit port in the well, theaspiration exit port providing aspiration fluid flow into the well andbeing located above a bottom of the well.
 30. The cassette of claim 29wherein the sheet comprises a molded aspiration fluid channel and amolded irrigation fluid channel.
 31. The cassette of claim 29 whereinthe sheet comprises a flexible, easily molded material.
 32. The cassetteof claim 31 wherein the sheet comprises silicone rubber or thermoplasticelastomer.
 33. The cassette of claim 29 wherein the fluid channel isplanar.
 34. The cassette of claim 29 wherein the fluid channel has atleast one transition region wherein the cross-sectional area of thefluid channel tapers.
 35. The cassette of claim 29 wherein the fluidchannel has at least one pinch valve site.
 36. The cassette of claim 29wherein the cassette further comprises a plurality of identifying tabsprojecting from the exterior of the body.
 37. The cassette of claim 29wherein the cassette further comprises at least one vent port in thepressure sensor well.
 38. A cassette, comprising: a) a body having anexterior; b) a relatively flexible sheet attached to the body, the sheetcontaining at least one molded fluid channel, the fluid channelprojecting outwardly from the exterior of the body and being in agenerally arcuate shape; c) an aspiration pressure sensor interface onthe exterior of the body, the interface having a well; and d) aplurality of alignment features in the exterior.
 39. The cassette ofclaim 38 wherein the sheet comprises a molded aspiration fluid channeland a molded irrigation fluid channel.
 40. The cassette of claim 38wherein the sheet comprises a flexible, easily molded material.
 41. Thecassette of claim 40 wherein the sheet comprises silicone rubber orthermoplastic elastomer.
 42. The cassette of claim 38 wherein the fluidchannel is planar.
 43. The cassette of claim 38 wherein the fluidchannel has at least one transition region wherein the cross-sectionalarea of the fluid channel tapers.
 44. The cassette of claim 38 whereinthe fluid channel has at least one pinch valve site.
 45. The cassette ofclaim 38 wherein the cassette further comprises a plurality ofidentifying tabs projecting from the exterior of the body.
 46. Thecassette of claim 38 wherein the cassette further comprises a pressuresensor well and an aspiration exit port located above a bottom of thewell.